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Biology - Unit 3 > Chapter 6 - Exchange > Flashcards

Chapter 6 - Exchange Flashcards

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1
Q

How do microorganisms obtain nutrients and remove waste?

A
  • Exchange via their surface
  • Nutrients moves in by diffusion
  • Waste moves out by diffusion
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2
Q

Why can microorganisms afford to perform exchange via their surface?

A
  • Large surface area to volume ratio
  • Short diffusion distance to all cells
  • Low demand
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3
Q

Why can’t animals and plants perform exchange via their surface?

A
  • Small surface area to volume ratio
  • Multicellular so there is a large diffusion pathway and high demand
  • Impermeable surfaces (to prevent pathogens) so require specialised exchange and transport systems
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4
Q

Distinguish between exchange system and transport system

A

An exchange system increases the rate of diffusion and a transport system delivers nutrients and removes waste from all cells

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5
Q

Summarise the structure of gills in fish

A
  • Fish have many gill filaments and gill lamellae for a large surface area
  • Gill lamellae have a thin wall so are permeable and have a short diffusion pathway
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6
Q

Give the features of a specialised exchange surface

A
  • Large compared to volume
  • Thin so diffusion distance short
  • Selectively permeable to allow selected materials to cross
  • Movement of the environmental medium away to maintain concentration gradient
  • Transport system to move internal medium to ensure concentration gradent maintained
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7
Q

What is the equation for diffusion

A

(SA x Difference in conc.) / Length of diffusion path

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8
Q

Summarise the structure of the tracheal system

A
  • Openings on body surface called spiracles
  • Valves open to allow gas exchange or close to prevent water loss
  • Spiracles connect to trachea
  • Trachea connect to tracheoles
  • Tracheoles connect to respiring cells and deliver O2, remove CO2
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9
Q

What are the three ways in which respiratory gases move in and out of the tracheal system?

A
  • Along diffusion gradient as O2 is used and CO2 produced
  • Mass transport as insects squeeze trachea enabling mass movement of air in and out
  • Ends of tracheoles filled with water. Lactate from anaerobic respiration occurs lowering water potential. Water moves from tracheoles due to osmosis and pulls air in due to decrease in volume. Final diffusion also in gas so more rapid
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10
Q

Define countercurrent flow

A

A mechanism by which the efficiency of exchange between two substances is increased by having them flow in opposite directions ensuring a maximum oxygen gradient is maintained across the full length of the lamellae

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11
Q

How is the structure of a leaf similar to that of an insect

A
  • All cells close to external air and hence a source of oxygen and carbon dioxide
  • Diffusion takes place in the gas phase making it more rapid than in water
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12
Q

What are the functions that help gaseous exchange occur in leaves?

A
  • Small pores called stomata ensure no cell far from external air so diffusion pathway short
  • Numerous interconnecting air spaces occur in mesophyll so gases come into contact with mesophyll
  • Large SA of mesophyll for rapid diffusion
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13
Q

How are stomata controlled and why?

A
  • Controlled by guard cells

- Control rate of gaseous exchange and close stomata to prevent water loss

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14
Q

How have insects evolved to reduce water loss?

A
  • Small SA:V ratio
  • Waterproof coverings of a rigid outerskeleton of chitin covered in waterproof cuticle
  • Spiracles that can be closed
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15
Q

How do plants limit water loss and why?

A
  • Cover leaves with waterproof coating

- Cannot have small SA as need to photosynthesise

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16
Q

Define xerophytes

A

Plants adapted to living in areas where water is in short supply

17
Q

State and describe xerophyte modifications

A
  • Thick cuticle = To reduce water loss
  • Rolling up of leaves = Traps regions of water with high water potential so no gradient
  • Hairy leaves = Hairs trap moist air with high water potential so no gradient
  • Stomata in pits or grooves = Trap moist air next to the leaf reducing water potential gradient
  • Reduced SA:V ratio = Reduces water loss as less area
18
Q

Why do mammals need to remove/obtain large amounts of gases?

A
  • Large organisms with many cells

- High temperature so high respiratory and metabolic rates

19
Q

Why are lungs located in the body?

A
  • Air is not dense enough to support and protect

- The body would lose water

20
Q

Summarise the components of the human gas exchange system

A
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
21
Q

Describe the process of inhalation

A
  • External intercostal muscles contract
  • Rib cage moves up and out
  • Diaphragm contracts and flattens
  • Increase in thorax volume, decrease in pressure
  • Air moves in
22
Q

Describe the process of exhalation

A
  • Internal intercostal muscles contract
  • Rib cages moves down and in
  • Diaphragm relaxes and bends back to a dome shape
  • Volume of thorax decreases so pressure increases
  • Air pushed out and aided by elastic recoil of alveoli
23
Q

What is the formula for Pulmonary ventilation

A

PV = Tidal volume x Ventilation rate

Tidal volume = Air breathed in/out in one breath
Ventilation rate = Number of breaths a minute
PV = Volume of air breathed in/out per minute

24
Q

Describe and explain diffusion of gas between alveoli and the blood

A
  • Red blood cells slowed as they pass through pulmonary capillaries allowing more time for diffusion
  • Distance between alveolar air and red blood cells reduced as cells flattened against wall
  • Wall of alveoli and capillary thin so short diffusion pathway
  • Alveoli and capillaries large SA
  • Breathing ventilation and heart rate maintains concentration gradient
25
Q

How are capillaries adapated for exchange?

A
  • One cell think (squamous epithelial cells) for short diffusion pathway
  • Narrow lumen increasing diffusion time and decreasing pathway
  • Circulation maintains gradient
  • Many for large SA
26
Q

Summarise the structure of trachea and bronchi

A
  • Wall made of cartilage
  • Strong to prevent collapse
  • C shaped for flexibility
  • Lining of goblet and ciliated epithelial cells
  • Mucus traps pathogens and cilia push out of lungs
27
Q

Summarise the structure of brinchioles

A
  • Walls made of smooth muscle
  • Contracts so lumen narrows and bronchiole constricts
  • Occurs near noxious gas to restrict how much reaches alveoli
  • Goblet and ciliated epithelial cells
28
Q

Summarise the major components of the digestive system

A
  • Oesophagus from mouth to stomach
  • Stomach with enzymes to digest
  • Ileum where food is digested and absorbed
  • Large intestine where water is absorbed
  • Rectum where faeces stored and excreted by egestion
  • Salivary glands that secrete amylase
  • Pancreas that secretes protease, lipase and amylase
29
Q

What is physical breakdown?

A
  • Occurs in mouth and food broken down to make it indigestible and increase SA for chemical digestion
  • Muscle in stomach also churns food and breaks it up
30
Q

What is chemical digestion

A
  • Digestion involving enzymes for hydrolysis of insoluble molecules into smaller soluble ones
31
Q

What are the three types of enzyme and what do they hydrolyse?

A
  • Carbohydrases such as amylase hydrolyse carbohydrates
  • Lipases hydrolyse lipids
  • Proteases hydrolyse proteins
32
Q

Summarise how a carbohydrate is digested

A
  • Salivary amylase in mouth hydrolyses starch
  • Food swallowed and low pH causes denturation
  • Food passed into small intestine where it mixes with pancreatic juice
  • This contains pancreatic amylase
  • Alkaline salts produced by pancreas and intestine wall for pH to be neutral
  • Muscle in intestine push food along
  • Membrane bound disaccharidase hydrolyses remaining maltose
33
Q

Summarise how a lipid is digested

A
  • Lipase produced by pancreas that hydrolyse ester bond
  • Form fatty acids and monoglycerides
  • Lipids split up into micelles by bile salts produced in the liver
  • Emulsification speeds up action of lipase by increasing SA
34
Q

Summarise how a protein is digested

A
  • Hydrolysed by peptidases
  • Endopeptidases hydrolyse bond between a protein molecule
  • Exopeptidases hydrolyse bond between terminal amino acid
  • Dipeptidases hydrolyse bond between a dipeptide
35
Q

How is the structure of the ileum adapted for diffusion?

A
  • Villi increase surface area and have a thin wall
  • Contain muscle which moves and mixes the context of the ileum, maintaining a gradient
  • Well supplied with blood to carry away absorbed molecules and maintain gradient
  • Microvilli increase surface area for absorption
36
Q

How are amino acids and monosaccharides absorbed

A
  • Sodium ions actively transported out of epithelial cell into blood by sodium potassium pump
  • Maintains gradient so sodium for lumen diffuses in to epithelial cells
  • As they diffuse in through a second carrier protein, they carry an amino acid or glucose molecule
  • These then pass into the blood by facilitated diffusion
37
Q

How are triglycerides absorbed in the ileum?

A
  • Monoglycerides and fatty acids remain with bile salts in lipid droplet
  • Micelles formed and come into contact with lining of epithelial cells
  • Micelles break down and release monoglycerides and fatty acids that are non polar so easily diffuse
  • Once inside, transported to endoplasmic recticulum to reform lipid
  • Golgi apparatus adds cholesterol and lipoproteins forming chylomicrons
  • Chylomicrons move out by exocytosis and enter the lacteal
  • They then pass into the blood

Biology - Unit 3 (1 decks)

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